1. Field of the Invention
The present invention relates to video compression. In particular, the present invention relates to a technique for encoding three-dimensional (3D) or stereo-view video sequences.
2. Description of the Related Art
Conventional video compression techniques typically handle three-dimensional (3D), or stereo-view video, in units of a frame. The most straightforward technique is to code each of the two views separately, as independent video sequences. This straightforward technique, however, suffers from a relatively poor coding efficiency and has a relatively higher complexity because two bit streams must be coded and decoded, multiplexed and demultiplexed and synchronized.
In order to reduce the complexity of handling two bitstreams, synchronized frames from each view can be grouped together to form a composite frame. The composite frame can then be coded into a single bitstream. The approach of using a composite frame, nevertheless, suffers from poor coding efficiency, and view-scalable functionality is lost. That is, the composite-frame approach does not allow a decoder to choose to decode and display only one of the two views of the 3D image.
Another approach for coding a 3D video image is disclosed by U.S. patent application Ser. No. 2002/0009137 A1 to Nelson et al., which discloses a system that codes a 3D video image into a base-layer bitstream and an enhancement-layer bitstream. The base-layer bitstream can include either the right view image or the left view image and is coded and decoded independently of the enhancement-layer bitstream. The enhancement-layer bitstream includes view images that are not included in the base-layer bitstream, and is dependent upon the base-layer bitstream for encoding and decoding purposes. The Nelson et al. approach not only has a better coding efficiency than conventionally encoding two view separately, but view-scalable functionality is preserved. The Nelson et al. approach, nevertheless, has a relatively higher complexity because multiple bitstreams (i.e., the base-layer bitstream and the enhancement-layer bitstream) must be handled.
Still another approach for coding a 3D video image is disclosed by U.S. patent application Ser. No. 10/817,309, to S. Lei et al., entitled “System And Method For Three-Dimensional Coding,” filed Apr. 2, 2004, which discloses a technique for coding stereo views using H.264 interlace video coding tools. The technique disclosed in U.S. patent application Ser. No. 10/817,309 will not, however, work for baseline profile applications because interlace video coding tools are only available for a decoder having the H.264 main profile or above. Consequently, in order for stereo-view sequences to be decoded by an H.264 baseline profile decoder, the stereo-view sequences must be conventionally coded as a pair of views forming a composite frame. Moreover, the video stream is not scalable and that the compression ratio is not optimal.
Consequently, what is needed is a technique for encoding a 3D sequence or a stereo-view sequence that can be decoded by an H.264 baseline profile decoder. Additionally, what is needed is a technique for encoding a 3D sequence or a stereo-view sequence that is view scalable, thereby allowing a 3D sequence or a stereo-view sequence to be decoded and/or viewed on a legacy two-dimensional (2D) display. Further, what is needed is a technique for encoding a 3D sequence or a stereo-view sequence that provides better coding efficiency than conventional techniques. Further still, what is needed is a technique for encoding a 3D sequence or a stereo-view sequence having flexible scalability.